Rod elevators have long been used to support sucker rods as they are run into and out of a well. Their basic design has remained substantially the same over that period of time. The elevator assembly is provided with a vertically oriented opening that extends out to one side of the assembly. The opening is larger than the diameter of the rod to allow the elevator to be positioned by moving it laterally onto the rod. Typically, the elevator includes an insert which also contains an opening aligned with the main elevator opening. Commonly, a standard size elevator is provided with a number of inserts of varying sizes, enabling a single elevator to be used to lift or lower sucker rods of different diameters. The width of the insert opening is somewhat smaller than the width of the elevator opening so as to fit more snugly about the sucker rod at the juncture between the elongated rod shaft and the thicker head portion. Thus when the elevator is raised, the insert structure surrounding the rod engages the bottom of the head portion of the rod to support the weight of the rod.
The heavy weight of the sucker rod against the small supporting area of the elevator insert during the rod raising or lowering operation causes high compressive forces to exist at this support area. In addition, if the elevator insert opening is not aligned with the rod during relative lateral movement between the rod and the elevator, the insert tends to scrape and bump against the rod during this operation. These actions are undesirable because they often result in damage to the plastic rod coating used to protect the metal rod against corrosion caused by contact with well bore fluids. If such coatings are damaged, the resulting corrosion will normally result in rod failure.
Since damage to the rod coating is inevitable when there is contact between the metal elevator and the sucker rod, repair procedures are commonly employed. This usually involves patching the rod coating by brushing a two-part epoxy onto the damaged area. The patch is not entirely effective, however, because of the difficulty in cleaning and drying the damaged area of the rod to the point required for proper adhesion of the epoxy.
Since the nature of the lifting operation is such that damage to the rod coating is likely to occur during the raising or lowering of sucker rods and since the conventional repair operation does not produce consistently acceptable results, some other means is needed to either better repair damaged rod coatings or prevent the damage from occurring in the first place.